Analyze the cause of the water bar and ink stick in the offset press
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The offset printing machine has water and ink bar failure during the printing process, which is a more difficult problem for the operator. Due to long-term overload operation, improper maintenance, the phenomenon of water and ink sticks is more prominent than high-speed machines. According to the work experience of the older generation of printing workers for many years, the phenomenon of water and ink stick appeared in the practice, and some simple analysis was made for the operator's reference.
In general, the offset printing machine has water and ink bars, which are caused by mechanical wear and are caused by improper adjustment. After the emergence of water and ink bars, we should look for the reasons from many aspects, carefully analyze them, and distinguish whether they are ink bars or water bars. We know that the ink bar is a random or regular dark line-like stripe on a certain printing surface or a graphic, with a width of about 5 to 8 mm, and the dot is enlarged; the water bar is an Internet point or figure on a certain printing surface. The text appears irregularly reduced light-colored linear stripes. Whether it is a water bar or a light bar, it will directly affect the quality of the product. Therefore, the operator should understand and master the main reasons for the production of the bar in order to solve it in time.
1. The roller gear is heavily worn by the drum gear. During the use of the machine, oil, paper dust and ink infiltrate into the teeth, and accumulate for a long time, and the top teeth phenomenon occurs. The plate cylinder and the blanket cylinder ask for excessive pressure, the gear gap is too small, and the gears cannot be accurately meshed with each other, that is, the hair is shaken during printing, and the roller surface generates large sliding friction. At this time, the ink bar with the same pitch of the gear may appear on the printing plate, and the dot or the graphic on the printing plate is easily damaged, and the printing durability is lowered.
2. The ink bar generated by the excessive pressure between the rollers. Many factories do not work on the machine's Sanping work, which seriously affects the quality of the products. Especially in the operation of the operator who has been operating for a long time, the pressure is increased blindly, and the rubber cloth and the plate pad are not carefully measured, and the vibration sound is obviously heard when the plate is pressed. We know that under normal pressure, the compression between the plate cylinder and the blanket cylinder should not exceed 0.1~0.15mm, and the compression of the blanket cylinder and the impression cylinder should not exceed 0.15~0.2mm. If the liner paper is randomly added, the pressure will be too large. Therefore, it is easy to produce ink sticks.
3. The ink stick produced by the impact of the bucket. The impact of the instantaneous vibration of the bucket on the impression cylinder of the machine is large. At this time, the drum is prone to instantaneous rapid change, and the gears on the drum are also subjected to the maximum force and easy to wear, and the long-term Produces a light bar. The position of the ink stick that appears on the printed sheet is generally fixed at 7 to 8 mm from the cornice. When this happens, the tipping bucket and the striker should be replaced, the position of the gear should be changed, the worn teeth should be staggered, and the spring force on the bucket should be loosened to avoid excessive vibration and reduce wear.
4. The rubber roller sorting does not cause the ink bar. Generally, there are four ink rollers in the 01 machine, and the diameter is different, in order to avoid the generation of the ink bar. For example, four inking rollers having a diameter of 81, 77, 76, and 79 mm should be arranged in a diameter of 81, 77, 76, and 79 mm from the front row. For example, when the rubber roller is loaded, the sorting is not correct or the pressure is improperly adjusted, and the ink stick is easily generated.
5. A toner bar caused by excessive pressure between the rubber rollers or the ink roller against the printing plate. When adjusting the pressure of the ink roller, not only the ink roller and the plate pressure should be carefully adjusted, but also the pressure between the ink rollers should be uniform. If the width of the one-sided indentation exceeds 6 mm, the ink bar is often produced on one side. Some small factories use 01 machine to print books and magazines, do not often scrape the rubber roller, the rubber roller is easy to aging and harden, and the printing plate has increased the relay force. When the roller is in the neutral position, it hits the edge of the mouth to produce an instantaneous jump, so the mouth is easy. Produce a more obvious ink stick. Therefore, when adjusting the pressure of the ink roller to the printing plate, it is necessary to press the ink roller in the order of the ink roller, and the ink mark width on the printing plate is 5, 5, 4 mm, and the two ends are parallel. .
6. The ink stick caused by the wear of the bridge gear. The two over-bridge gears of the ink-jet roller are equipped with an eccentric device. After adjusting, the screws must be locked and a certain gap is left. If it is too tight, it will generate noise. If the lubrication is not in place, and there are dirt and oil between the teeth, the gear will be seriously worn, resulting in inaccurate gear meshing, the squeezing roller will be shaken, and the printing plate will have obvious ink stick.
7. The ink roller caused by the aging of the rubber roller. In the printing house where book-based activities are the mainstay, if the offset printing machine operator does not wash the rubber roller frequently, the ink is accumulated on the rubber roller for a long time, and the dust in the paper penetrates the surface of the rubber roller, and the surface is broken and cracked after the friction occurs. The luminescence becomes hard, the performance of the rubber roller is reduced, and a clear ink stick is produced. If the aging of the rubber roller is not serious, only a bright film is formed on the surface, the rubber roller can be removed, the surface is lightly rubbed with pumice powder, and the surface ink is completely removed, and the ink stick disappears or is lightened. If the rubber roller is seriously aging, there is no elasticity. When the rubber roller is slippery during operation, the rubber roller must be replaced.
8. The ink bar generated by vibration. The neutral of the machine drum is large, and the pressure between any two rollers in operation constantly disappears in the neutral position and appears at the entrance. The impact of the roller entering and exiting forms a vibration source, especially the vibration generated by the impact of the bucket. Therefore, the existence of the vibration source of the offset printing machine is the main cause of the vibration bar. When the machine is in normal operation, these vibration sources instantaneously break the uniform rotation between the rollers. Once the vibrating bar is found, the source of vibration should be found first, and the problem of the lower ring will be complicated and simple.
9. The ink bar generated by the printing pressure between the plate cylinder and the blanket cylinder, the blanket cylinder and the impression cylinder is too large. In theory, most of the printing plate and rubber stencils have a print width of 4 to 6 mm, and the width between the blanket cylinder and the impression cylinder is 5 to 7 mm, but the operator adjusts the center distance accurately to the collar. The amount is not accurate, and it is found that the imprint is not real, and the liner paper is added at will. Sometimes the blanket is not stretched tightly. When the pressure is high, the rubber will appear on the blanket like a washboard.
10. Ink bars caused by other causes. If the ink is too thin, the viscosity is small, the bar is easy to be released, the offset paper is easy to produce the ink bar when printing on the ground or the wire, the blue ink is easy to produce the ink bar in the dark ink, the thickness of the pad is uneven, the quality of the blanket is poor, and so on. .
11. The water bar is also called the white bar. The water bar generated on the low speed machine is generally caused by the contact pressure of the water roller on the printing plate. It is characterized in that the plate mouth is bright and has a fixed bar. The water supply mechanism of the offset printing machine is cam-controlled and transmits water in the neutral position of the plate cylinder. The position of the control roller of the water transfer roller and the contact time of the printing plate should be properly adjusted, and the appropriate pressure should be adopted. In general, the machine has two water rollers. As long as the adjustment is good, only one plate roller can be used. It is observed that the following one is generally used, but when changing the water roller, the operator points the machine to the neutral position and uses the crowbar to pry the water roller, so that the water roller bracket is easy to loose or cause the water roller to deform, so the above one is used. The root is more suitable to prevent the production of water bars.
12. In production, we also found that the water bar is generated when the pressure between the ink roller and the ink roller is light. This is because the pressure between the ink rollers is too light, the ink cannot be uniformly transferred on the rubber roller, and floats on the rubber roller. When the ink is unbalanced, the ink is emulsified due to the thickening of the ink layer on the surface of the rubber roller, and the water bar is likely to appear on the printed sheet.
13. The water roller caused by the vibration of the water roller is too large. The machine water roller swing frame is controlled by a cam, and the machine uses a long cam wear. The beating occurs in the neutral position, the water bar is more obvious, and most of the printing is about 5,000 sheets, so that the water bar appears, and the printing plate's printing durability is lowered.
14. The quality of the water roller cover is poor, the local unevenness, the water-filling roller package is not tight, the two ends are tight in the middle, the water supply is uneven or the water volume is too large, and the water bar is easy to appear in the front line of the mouth.
In short, when the machine you are operating has a water-jet bar, you must analyze it from many aspects, and clarify it step by step. As long as it is handled properly, you will be able to get a satisfactory solution.